1. Field of the Invention
The present invention relates to a catheter, especially a flexible pressure-limiting or zero-pressure balloon catheter and a method for using the catheter.
2. Description of Related Prior Art
A number of conventional balloon catheters exist in the prior art. Some catheters are used to drain the bladder of a patient during surgical procedure or to treat bladder and/or urethra or prostate conditions, for example. For example, a common balloon catheter made by RUSCH® and referred to as a Foley catheter is widely used today for treating and draining a patient's bladder. The Foley catheter is shown in FIG. 1 and has a multi-lumen shaft 1 that is disposed in the urethra 10, a balloon portion 3 disposed at the distal end of the shaft 1, a fluid drain section 4 disposed at the distal end of the balloon 3, and a curved, distal guiding tip 5 at the distal-most end of the entire catheter. When placed properly, the proximal-most side of the inflated balloon 3 rests on the interior wall 31 of the bladder 30, entirely blocking off the urethrovesical junction 11 connecting the bladder 30 and the urethra 10. In such a position, the fluid drain section 4 allows continuous drainage of the bladder 30 and the balloon 3 virtually entirely prevents the catheter from slipping out of the bladder. This ideally inserted position is shown in FIG. 1. As used herein, a fluid can be either a liquid or a gas. Exemplary fluids for inflating a balloon 3 are saline, air, or carbon dioxide gas. Exemplary fluids drained by the catheters mentioned herein include urine and blood.
Basically, the catheter has tube-like body with two lumens passing therethrough. The larger lumen 120 (see FIG. 2) is open to the bladder (distally) and empties into an ex-corporeal bag (proximally) for eventual disposal. A smaller lumen 130 is used to inflate the balloon 3 with water (typically) using a syringe attached to the inflation lumen fitting 260. When inflated in the bladder, for example, the catheter is prevented from sliding out of the urethra in use.
Over 96 million indwelling catheters are sold worldwide on an annual basis. Twenty four million catheters are sold to hospitals in the U.S. There are numerous complications associated with those catheters that need to be prevented. These complications are responsible for increases in hospital stays, excessive bleeding, mortality, as well as morbidity. They also cause an increased expense and burden on the already-stressed health care system.
The complications result from several different mechanisms. First, and probably most common, is improper placement of the catheter. Because of the unique anatomy of the male urethra, placing a urethral catheter for urinary drainage can be difficult. A problem arises when the physician, technician, or nurse thinks that the catheter is actually in a proper position when it is not. The proper position for the catheter is with the balloon located in the cavity of the bladder. In this position, the tip distal to the balloon is located in the bladder and is used to drain the bladder cavity.
For placement of this catheter in the bladder 30 in the ideal position, however, the physician or technician has no visual aid. As shown in FIG. 1, the wall 40 defining the urethrovesical junction 11 is very short in the longitudinal direction of the urethra 10. If the physician inserts the catheter too far into the bladder 30, no damage occurs from balloon inflation; however, there is a possibility of leakage around the balloon 3, which, under normal conditions, helps to lubricate the urethra 10. In such a case, gentle proximal movement will move the proximal side of the balloon 3 against the urethrovesical junction 11. The bladder 30 can then easily expand and stretch to compensate for the balloon 3. A normal bladder capacity is 400 to 500 cc. A normal balloon capacity is approximately 10 to 12 cc although larger balloons are sometimes used. A typical balloon is 5 cc, however, most clinicians put 10 cc of water in the balloon to inflate it. With 5 cc of water in the balloon, the diameter is approximately 2 cm and, with 10 cc, the diameter is approximately 2.5 cm.
The complication occurs when the technician and/or nurse inflates the balloon when the balloon is not in the bladder. If the technician does not insert the catheter in far enough, then the balloon 3 will be inflated within the urethra 10—a condition that is common and, not only is it to be avoided at all costs, is a frequent cause of bladder infections created during a hospital or clinic visit. Infections arise because inflation of the bladder 3 inside the urethra 10 causes the urethra 10 to stretch too far and tear. Even though the urethra 10 is a flexible tube, it has limits to which it can be safely stretched from within. Almost every balloon catheter has a balloon outer diameter/circumference that well-exceeds the safe stretching limit of the urethra 10. Therefore, if the balloon catheter is not inserted far enough, inflation of the balloon 3 will cause serious injury to the urethra 10. This is especially true with elderly patients who have urethra 10 that are not as elastic as younger patients. Also, just as important is the change in anatomy of older males, in particular, the prostatic portion of the urethra. With age, the prostate becomes larger and, sometimes, the catheter cannot be advanced through the prostatic portion of the urethra. When this occurs, the technician does not insert the catheter all the way into the bladder and inflates the balloon within the urethra, causing severe bleeding and damage.
The elastomeric balloon of present-day catheter products requires relatively high pressures to initiate inflation and expand to an expected full-diameter shape upon over-inflation. As such, when incorrectly placed in the urethra, the rapid inflation, combined with the high-pressure, causes the balloon to tear the surrounding membrane, called the mucosa. Tearing of the urethra 10 in this way causes bleeding and allows bacteria to enter into the bloodstream at the tear site, thus causing the subsequent bladder infection. Significant bleeding can become life threatening. The urethra can normally dilate several millimeters; however, when the balloon is inflated, this dilation is usually several centimeters. Also, without sufficient and immediate venting of the balloon inflation fluid after placement, an accidental or intentional pull on the catheter externally can and does cause extensive bodily harm to a patient fitted with the device.
Life threatening bleeds, especially in patients who are anticoagulated, can and do occur. Also when the urine is infected, as in immunocompromised patients and the elderly, the bacteria enter the blood stream and can cause serious infections (e.g., sepsis), which frequently can lead to death. If the patient survives the initial trauma, then long-term complications, such as strictures, can and usually do occur. Strictures are narrowings within the urine channel and usually require additional procedures and surgeries to correct.
Other mechanisms of catheter-induced injuries are inadvertent manipulation of the tubing or dislodging of the balloon—caused when the catheter is pulled from outside the patient due to a sudden jerk or tension. This commonly happens when the patient is ambulating or traveling from the bed to the commode or bathroom. The tubing may inadvertently become fixed while the patient is still moving, at which time a sudden jerk is imparted upon the balloon and pulls the balloon into the urethra to tear it, causing severe pain and bleeding. Injury caused by the improper, inadvertent, and/or early removal of an inflated balloon catheter is referred to as iatrogenic injury (also referred to as an in-hospital injury). Hundreds of thousands of such iatrogenic injuries occur each year—all of which need to be prevented, not only for patient safety, but also because the cost imposed on the medical health industry for each injury is enormous.
Yet another scenario occurs when the patient deliberately pulls on the catheter, thereby causing self-induced pain and injury to the urethra. This commonly happens in confused patients, for example, patients in nursing homes who have a disease or cognitive dysfunction problem, such as Alzheimer's disease, or other diseases that make the patient unable to understand the necessity of having a catheter. Confusion occurs when the patient has a spasm causing a strong urge to urinate and pain. During the spasm, the confused patient often tugs and pulls on a catheter, which results in injury. Like iatrogenic injuries, these self-induced injuries must be prevented.
The injuries mentioned herein are not limited to males and also cause severe damage to the female bladder and urethra. The injuries can also occur post-surgically, which makes the damage even more severe. One common situation where injury is caused is when the patient is medicated with morphine or other analgesics that render the patient confused and unable to make rational decisions. Feeling the foreign body inside the urethra, the confused patient does not know to leave it alone and, instead, gives it the injury-causing tug. These injuries have been well-documented and are not limited to adults. Numerous injuries are documented in pediatric patients.
Usually, it takes time to make a diagnosis of patient-caused catheter injury. Immediately after diagnosing the injury, a technician needs to deflate the catheter. However, once the urethra is torn, replacing the damaged catheter with another catheter is quite difficult and, in fact, exacerbates the injury. Sometimes, the patient has to be taken to the operating room to replace a urinary drainage tube once the injury occurs. Because catheters and leg bags are now used routinely in certain situations during home health care, this scenario is not limited to hospitals and occurs at nursing homes and patients' homes.
Most of the recent catheter technology has been focused on reducing urinary tract infections that are caused by catheters, injuries that are usually the most common catheter-related complications.
In a conventional balloon 3, the balloon 3 has a substantially constant balloon wall thickness. The balloon 3 is fixed to the outer surface of a fluid drainage line (not illustrated in FIG. 1) and is not intended to be removed therefrom or to burst thereon unless an extraordinary amount of inflation occurs. If such an event happens, the material of the balloon will open at a random location based upon the microscopic fractures or weaknesses in the material itself. Such a tearing event is not supposed to occur under any circumstances during use with a patient.
Prior art catheters are not constructed to prevent tearing of the urethra during a catheter implanting procedure and are not constructed to break in any predefined way. Accordingly, it would be beneficial to provide a balloon catheter that does not inflate past the tearing limit of a urethra and deflates in a desired, predefined way under certain conditions.